Gap Sensing Via Engine Coil

Abstract

A haptic engine for an electronic device includes a coil assembly and a stator. The coil assembly may be coupled to an input structure, such as a button cap. In an gap sensing mode, a first voltage may be driven through the coil assembly to determine an impedance of the coil assembly. The impedance is then used to determine a gap between the coil assembly and the stator. In a haptic drive mode, a second voltage is driven through the coil assembly to produce a haptic output.

What is claimed is: 
     
         1 . An electronic device comprising:
 a plurality of housing elements;   an input structure at least partially moveable with respect to at least one housing element of the plurality of housing elements;   a coil assembly mechanically coupled to the input structure such that movement of the input structure causes movement of the coil assembly;   a stator having a surface that is separated by a gap from a surface of the coil assembly; and   a circuit operatively coupled to a processor, the circuit and the processor configured to:
 drive a first signal through the coil assembly; and 
 determine a distance of the gap based at least in part on an impedance of the coil assembly when driving the first signal through the coil assembly. 
   
     
     
         2 . The electronic device of  claim 1 , wherein:
 the stator is mechanically coupled to a button such that movement of the button causes movement of the stator; and   the coil assembly is connected within a housing defined by the plurality of housing elements with the surface of the coil assembly separated from the surface of the stator, forming the gap.   
     
     
         3 . The electronic device of  claim 1 , wherein the circuit and the processor are further configured to:
 drive a second signal different from the first signal through the coil assembly; wherein:   a power of the second signal is based at least in part on the determined distance of the gap.   
     
     
         4 . The electronic device of  claim 3 , wherein:
 the second signal is a single ended signal.   
     
     
         5 . The electronic device of  claim 3 , wherein:
 the second signal has a frequency different from the first signal.   
     
     
         6 . The electronic device of  claim 1 , further comprising:
 a force sensor mechanically coupled to the coil assembly and electrically coupled to the circuit; wherein the circuit and the processor are further configured to:   determine the distance of the gap based at least in part on a signal from the force sensor.   
     
     
         7 . The electronic device of  claim 1 , wherein:
 the circuit comprises a sense resistor electrically coupled with the coil assembly.   
     
     
         8 . The electronic device of  claim 7 , wherein:
 the impedance of the coil assembly is based at least in part on a value of current detected through the sense resistor when driving the first signal through the coil assembly.   
     
     
         9 . The electronic device of  claim 7 , wherein the circuit and the processor are further configured to:
 switch current from a first path to a second path; wherein:   the first path includes the coil assembly electrically coupled to the sense resistor; and   the second path includes the coil assembly electrically coupled to ground.   
     
     
         10 . The electronic device of  claim 1 , wherein:
 the circuit comprises a first sense resistor and a second sense resistor.   
     
     
         11 . The electronic device of  claim 10 , wherein the circuit and the processor are further configured to:
 switch current from a first path to a second path; wherein:   the first path includes the coil assembly electrically coupled to the first sense resistor and electrically isolated from the second sense resistor; and   the second path includes the coil assembly electrically coupled to the second sense resistor and electrically isolated from the first sense resistor.   
     
     
         12 . The electronic device of  claim 1 , wherein:
 the first signal is an alternating current signal.   
     
     
         13 . A device comprising:
 a housing defining an opening;   a button positioned at least partially within the opening and moveable with respect to the housing;   a coil assembly comprising a casing, and a coil disposed in the casing, the coil assembly mechanically coupled to the button such that movement of the button causes movement of the coil assembly;   a stator connected within the housing with a surface of the stator separated from a surface of the casing, forming a gap;   one or more force sensors mechanically coupled to one or both of the button or the coil assembly; and   a flexible printed circuit board disposed within the housing; wherein:   one or more first wires connect the flexible printed circuit board to the coil; and   one or more second wires connect the flexible printed circuit board to the one or more force sensors.   
     
     
         14 . The device of  claim 13 , wherein:
 the stator is mechanically coupled to a button such that movement of the button causes movement of the stator; and   the coil assembly is connected within the housing with a surface of the coil assembly separated from the surface of the stator, forming the gap.   
     
     
         15 . The device of  claim 13 , wherein the flexible printed circuit board comprises voltage common mode buffer circuitry. 
     
     
         16 . The device of  claim 13 , wherein the flexible printed circuit board comprises an analog-to-digital converter circuit and a digital signal processing circuit. 
     
     
         17 . The device of  claim 13 , further comprising:
 a processor operatively coupled to the flexible printed circuit board, the processor and the flexible printed circuit board configured to:
 drive a first signal through the coil assembly; and 
 determine a distance of the gap based at least in part on an impedance of the coil assembly when driving the first signal through the coil assembly. 
   
     
     
         18 . A method of sensing a gap via a reluctance engine coil, for controlling haptic output, comprising:
 switching a circuit from a haptic drive mode to an inductive sensing mode;   applying, via the circuit in the inductive sensing mode, a first signal to the reluctance engine coil;   measuring, via the circuit in the inductive sensing mode, an inductance and resistance of the reluctance engine coil, the measuring based at least in part on the first signal;   determining, via the circuit in the inductive sensing mode, a distance of the gap associated with the reluctance engine coil and a stator based at least in part on the measured inductance and measured resistance; and   switching the circuit from the inductive sensing mode to the haptic drive mode.   
     
     
         19 . The method of  claim 18 , further comprising:
 applying, via the circuit in the haptic drive mode, a second signal different from the first signal to the reluctance engine coil; wherein:   a power of the second signal is based at least in part on the determined distance of the gap.   
     
     
         20 . The method of  claim 18 , further comprising:
 measuring a voltage from a force sensor mechanically coupled to the reluctance engine coil; and wherein determining the distance of the gap comprises:   determining the distance of the gap associated with the reluctance engine coil and the stator based at least in part on the measured inductance, measured resistance, and the measured voltage.